- 标题
- 摘要
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- 实验方案
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High Resolution and Fast Processing of Spectral Reconstruction in Fourier Transform Imaging Spectroscopy
摘要： High-resolution spectrum estimation has continually attracted great attention in spectrum reconstruction based on Fourier transform imaging spectroscopy (FTIS). In this paper, a parallel solution for interference data processing using high-resolution spectrum estimation is proposed to reconstruct the spectrum in a fast high-resolution way. In batch processing, we use high-performance parallel-computing on the graphics processing unit (GPU) for higher efficiency and lower operation time. In addition, a parallel processing mechanism is designed for our parallel algorithm to obtain higher performance. At the same time, other solving algorithms for the modern spectrum estimation model are introduced for discussion and comparison. We compare traditional high-resolution solving algorithms running on the central processing unit (CPU) and the parallel algorithm on the GPU for processing the interferogram. The experimental results illustrate that runtime is reduced by about 70% using our parallel solution, and the GPU has a great advantage in processing large data and accelerating applications.
关键词： parallel computing,high performance,GPU,Fourier transform imaging spectrometer,spectrum reconstruction
更新于2025-09-23 15:22:29
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Comparison of basis functions and q-space sampling schemes for robust compressed sensing reconstruction accelerating diffusion spectrum imaging
摘要： Time constraints placed on magnetic resonance imaging often restrict the application of advanced diffusion MRI (dMRI) protocols in clinical practice and in high throughput research studies. Therefore, acquisition strategies for accelerated dMRI have been investigated to allow for the collection of versatile and high quality imaging data, even if stringent scan time limits are imposed. Diffusion spectrum imaging (DSI), an advanced acquisition strategy that allows for a high resolution of intra-voxel microstructure, can be sufficiently accelerated by means of compressed sensing (CS) theory. CS theory describes a framework for the efficient collection of fewer samples of a data set than conventionally required followed by robust reconstruction to recover the full data set from sparse measurements. For an accurate recovery of DSI data, a suitable acquisition scheme for sparse q-space sampling and the sensing and sparsifying bases for CS reconstruction need to be selected. In this work we explore three different types of q-space undersampling schemes and two frameworks for CS reconstruction based on either Fourier or SHORE basis functions. After CS recovery, diffusion and microstructural parameters and orientational information are estimated from the reconstructed data by means of state-of-the-art processing techniques for dMRI analysis. By means of simulation, diffusion phantom and in vivo DSI data, an isotropic distribution of q-space samples was found to be optimal for sparse DSI. The CS reconstruction results indicate superior performance of Fourier-based CS-DSI compared to the SHORE-based approach. Based on these findings we outline an experimental design for accelerated DSI and robust CS reconstruction of the sparse measurements that is suitable for the application within time-limited studies.
关键词： diffusion MRI,sparse acquisition,q-space undersampling,microstructure,compressed sensing,basis functions,diffusion spectrum imaging
更新于2025-09-23 15:22:29
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A Highly Birefringent and Nonlinear AsSe<formula><tex>$_{2}$</tex></formula>-As<formula><tex>$_{2}$</tex></formula>S<formula><tex>$_{5}$</tex></formula> Photonic Crystal Fiber with Two Zero-Dispersion Wavelengths
摘要： A hybrid AsSe2–As2S5 photonic crystal ?ber (PCF) with a solid elliptical core is proposed and studied theoretically by the full-vector ?nite element method. The core and cladding of the PCF are made of AsSe2 and As2S5 glasses, respectively. Simulation results demonstrates that, at the operating wavelength of 1.55 μm, the proposed PCF not only exhibits a very high birefringence of 0.091 but also has large nonlinear coef?cients of 147.8 and 78.2 W ?1m ?1 for the X- and Y-polarized (X and Y-pol) modes, respectively. Moreover, it is able to achieve two zero-dispersion wavelengths for both the X-pol (1.52 and 2.19 μm) and Y-pol (1.43 and 2.12 μm) modes. The proposed hybrid PCF exhibits excellent polarization maintaining and the nonlinearity performance, thus, suitable to be used in supercontinuum spectrum generation and polarization maintaining nonlinear signal processing.
关键词： zero-dispersion wavelength,High birefringence,supercontinuum spectrum generation,photonic crystal ?ber,nonlinearity
更新于2025-09-23 15:22:29
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Electronic properties of graphene with point defects
摘要： This article attempts a point-by-point review of the electron spectrum of graphene containing defects (adsorbed atoms, substitutional atoms, vacancies) that can be adequately described within the Lifshitz model. In this regard, the known Hamiltonian for this model is calculated for the case of two-dimensional relativistic electrons, and the criteria for occurrence of an impurity resonance near a Dirac point are given. The theory of concentration band structure transformation of graphene is presented, from which it follows that a transport gap is opened upon reaching a strictly defined value of impurity concentration in the neighborhood of the energy of impurity resonance. At the same time, the question of the possibility (or impossibility) of localization in such a {spatially disordered system} of Dirac quasiparticles is analyzed. Based on this, it is possible to provide an explanation and present a description of a phenomenon recently observed in {impure graphene}, the metal-dielectric transition that appears as a direct consequence of the decrease of the Fermi energy of the system in the region of a transport gap. The concept of local spectrum rearrangement of graphene, which also occurs during the process of increased concentration of defects in it, is introduced and substantiated. Physical reasons are formulated, by which the position of the minimum of the low-temperature conductivity of graphene as a function of the Fermi energy of electrons corresponds to the impurity resonance energy rather than to the Dirac point, as has been validated in a number of theoretical and test studies. Here, it appears that the minimum value is not a universal magnitude, but depends on the concentration of defects. Analytical examination of impurity effects is accompanied by numerical modeling of the system under study, as a result of which complete correspondence has been established between these two approaches. In particular, the overall picture of spectrum rearrangement, localization of electron states, and also the effects having local nature are confirmed.
关键词： electron spectrum,transport gap,Lifshitz model,impurity resonance,metal-dielectric transition,graphene,local spectrum rearrangement,conductivity,point defects
更新于2025-09-23 15:21:21
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On spectrum assignment in elastic optical tree-networks
摘要： To face the explosion of the Internet traffic, a new generation of optical networks is being developed; the Elastic Optical Networks (EONs). EONs use the optical spectrum efficiently and flexibly, but that gives rise to more difficulty in the resource allocation problems. In this article, we study the problem of Spectrum Assignment (SA) in Elastic Optical Tree-Networks. Given a set of traffic requests with their routing paths (unique in the case of trees) and their spectrum demand, a spectrum assignment consists in allocating to each request an interval of consecutive slots (spectrum units) such that a slot on a given link can be used by at most one request. The objective of the SA problem is to find an assignment minimizing the total number of spectrum slots to be used. We prove that SA is NP-hard in undirected stars of 3 links and in directed stars of 4 links, and show that it can be approximated within a factor of 4 in general stars. Afterwards, we use the equivalence of SA with a graph coloring problem (interval coloring) to find constant-factor approximation algorithms for SA on binary trees with special demand profiles.
关键词： Chordal graphs,Elastic optical networks,Interval coloring,Spectrum assignment
更新于2025-09-23 15:21:21
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Effects of inter-subband couplings on bound and extended states of terahertz cascade structures
摘要： We theoretically analyze the effect of inter-subband couplings on the eigenstates of a terahertz heterostructure in the presence of coulombic donors. We find that the inter-subband electron-donor interaction causes a drastic reorganization of the eigenenergies and a strong admixture between the subbands that decisively influences the optical absorption spectrum of the structure. These results illustrate the importance of the inter-subband couplings in the formulation of the eigenstates of imperfect terahertz heterostructures.
关键词： inter-subband couplings,eigenstates,terahertz cascade structures,optical absorption spectrum
更新于2025-09-23 15:21:21
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - Multi point strain and temperature sensing based on Brillouin optical time domain reflectometry
摘要： In this paper, multiple points of strain and temperature measurement in real-time is investigated using a Brillouin optical time domain reflectometry (BOTDR) system. The Brillouin frequency shift (BFS) is analysed with strain and temperature effects applied at various locations of the sensing fibre. In addition, a passive depolarizer was employed in order to reduce the polarization noise. The strain and temperature coefficients are found to be 0.79 MHz/oC and 0.057 MHz/με.
关键词： Brillouin gain spectrum,strain measurement,temperature measurement
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Investigation of Doppler Spectra of Sea Backscatter Through Large-Scale Monte Carlo Simulations: Direct Numerical Solution And Approximate Models
摘要： The study simulates and analyses backscattering of a time-harmonic (continuous-wave) X-band signal from evolving ocean-like surfaces in the 2D space. For the same surface realization, the scattered field is evaluated using the direct numerical solution of a first-principles boundary integral equation, and with two approximate models: the coherent Two-Scale Model (CTSM) and the second-order Small Slope Approximation (SSA2). Large Monte Carlo ensembles are built up to evaluate well-averaged Doppler spectra. The investigation focuses on the two spectral parameters: centroid and width, with alternative definitions for the latter being discussed. A broad and finely sampled range of incidence angles is considered, providing a comprehensive and detailed view at the behavior of these quantities from nadir to low grazing. Using the same set of surfaces when calculating backscattered fields according to the exact and approximate methods provides a rigorous test for the accuracy of the chosen scattering models. The reported high-quality data from direct numerical simulations can serve as a benchmark for other scattering formulations.
关键词： numerical simulations,sea surface electromagnetic scattering,Doppler spectrum
更新于2025-09-23 15:21:21
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Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range
摘要： In this paper, we present a new FTIR-based micro?uidic system for Glucose, Fructose and Sucrose detection. The proposed micro?uidic system is based on a pseudo-continuous ?ow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm?1 of the Mid-IR region. The proposed pseudo-continuous ?ow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements.
关键词： mid-IR absorption spectroscopy,absorption spectrum,FTIR spectroscopy,microscopy-FTIR spectrometer,sugars detection and quanti?cation,Glucose,Fructose,Sucrose,pseudo-continuous ?ow
更新于2025-09-23 15:21:21
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A Novel Recovery Method of Soft X-ray Spectrum Unfolding Based on Compressive Sensing
摘要： In the experiment of inertial con?nement fusion, soft X-ray spectrum unfolding can provide important information to optimize the design of the laser and target. As the laser beams increase, there are limited locations for installing detection channels to obtain measurements, and the soft X-ray spectrum can be dif?cult to recover. In this paper, a novel recovery method of soft X-ray spectrum unfolding based on compressive sensing is proposed, in which (1) the spectrum recovery is formulated as a problem of accurate signal recovery from very few measurements (i.e., compressive sensing), and (2) the proper basis atoms are selected adaptively over a Legendre orthogonal basis dictionary with a large size and Lasso regression in the sense of (cid:96)1 norm, which enables the spectrum to be accurately recovered with little measured data from the limited detection channels. Finally, the presented approach is validated with experimental data. The results show that it can still achieve comparable accuracy from only 8 spectrometer detection channels as it has previously done from 14 detection channels. This means that the presented approach is capable of recovering spectrum from the data of limited detection channels, and it can be used to save more space for other detectors.
关键词： spectral measurement,spectrum unfolding,sparse representation,soft X-ray spectrometer,compressive sensing,lasso regression
更新于2025-09-23 15:21:21